This application relates to an apparatus and a method for measuring a position of a moving component within a very small difference from an end of travel position.
Modern systems are becoming more and more precise. One such system is an actuator for moving components. Example components could be any number of components on an aircraft application. So-called linear variable displacement transducers (LVDTs) monitor a position of a surface in the actuator to provide the feedback to a control of that position. The control may control a motor for the actuator such that the actuator can be assured to move the component to a desired position.
One such LVDT utilizes ultrasonic waves bounced off a surface on a component in the actuator. Such systems provide very good accuracy for position feedback.
However, it is known that when the distance to the target surface becomes very small, the ultrasonic measuring device can have signal interference. In particular, the sensor generally works by sending an outgoing signal which reflects off of a target surface and back to the sensor. The time of this travel is monitored to provide the position feedback.
When the distance becomes less than a minimum distance, the outgoing signal can interfere with the incoming reflected signal.
The minimum difference varies by the frequency of the signal and the speed of sound in the medium through which the signal is traveling. As one example, there is a five millimeter minimum distance from a target utilizing a 2.5 megahertz transducer in a water medium.